Numerous sealing screw devices having a safety means intended to control access to the contents are known of the container closed by these devices, and to prevent, in particular, fraudulent handling of these contents.
Generally, these sealing devices which are fitted on bottles whose rings are of the almost universally standardized type known under the name "Pilferproof" have a screw cap, possibly provided with a seal, and an annular safety strip that can be separated at the lower part from the skirt of the cap. Any attempt to unscrew the cap must cause the separation of the safety strip.
Originally, these tamper-proof caps were made of metal, particularly aluminum and, after screwing on the cap, the safety strip was crimped on the neck by a simple mechanical device.
At the present time, there is a tendency to replace aluminum with thermoplastic polymers which are no longer suited to a simple crimping because of their natural elasticity,
Therefore, a certain number of solutions have been devised to provide a crimping of the tamper-proof strip.
In French Pat. Nos. 2,282,378 and 2,467,790, heat-shrinking of the tamper-proof strip under the action of the jet of hot air is performed.
This solution involves adding an additional stage to the bottling and capping lines, and exhibits the risk of total melting of the seals when the line stops, which necessitates providing a safety device. Further, the appearance of the shrunken strip often leaves something to be desired.
In French Pat. No. 2,349,140, the tamper-proof strip is folded toward the inside of the cap when it is screwed on the neck of a bottle, so that its upper edge strikes against a projection of the neck. During unscrewing, the strip thus locked cannot rise and is separated from the skirt. But there is a danger that the strip will be pulled out without separating.